42 MISCELLANEOUS PAPEES. 



Table IV. — Percentage of parasitism of Thrips tabaci by Thripoctenus russelli at 



Compton, Cal., 1911. 



In October, from the pupiB of this parasite sent to Washington, 

 D. C, from Compton, Cal., adults were reared which, when placed in 

 vials with larvsB of Tlirips tabaci, immediately began to oviposit in 

 them. Unfortunately the parasitized larvse soon died, the parasites 

 perishing with them, and but few data were secured from this ex- 

 periment. It is possible that this mortality of the host was due to 

 the cool weather which prevailed at the time of the experiment. 



These experiments demonstrate the important fact that the 

 parasite Thripoctenus will ovi])osit in the larvae of Tlirips tabaci. 

 This later may be an important asset in the control of this destructive 



insect. 



Euthrips tritici Fitch. 



Adults of Thripoctenus, when confined with larvae of Euthrips 

 tritici Fitch, immediately commenced ovi position. As a result, 

 although the larvse of this tlirips are more difficult to rear, the parasite 

 was successfully reared in a number of experiments. No evidence 

 of parasitism in the open was observed for this species, but as the 

 larvae were at no time very abundant, sufficient data were not secured 

 to determine whether this insect was being parasitized in the field. 



Heliothrips haemorrhoidalis Bouche. 



A series of experiments was conducted in which the larva of 

 Heliothrips hsemorrhoidalis Bouche was confined with this parasite 

 and in every case oviposition was noted many times. However, 

 with the exception of one doubtful example, no indication of para- 

 sitism ever appeared. To account for this failure is impossible at 

 the present time unless it was that the host larvas were in a far too 

 advanced state. 



Heliothrips Jemoratis Reuter. 



Adults of Thripoctenus russelli that emerged in Washington on 

 October 2, 1911, were confined with the larvse of Heliothrips femoralis 

 Renter and they immediately commenced oviposition. These 



